Trace Element Analysis of Soil Samples From Mui Basin, Kitui County for Mineral Content Evaluation Using Multivariate Statistics

Abstract

The importance of minerals for economic development and sustainability of a country cannot be ignored in modern society. However, mineral exploration in deeply weathered environments is often hampered by significant depths, greater than five meters, of weathered or transported material over mineralized bedrock. Nonetheless, mineral exploration in thick vegetation cover can be undertaken by evaluating trace elements levels in underlying soils. In Kenya however, there exists limited studies on geochemical mapping. The main aim of this study was therefore, to identify selected trace elements in block C of Mui basin, Kitui County on an area of 131 Km2, identified as Yoonye, Kateiko and Kathonzweni and to use multivariate analyses on the data set to determine mineral content of buried ores. Seven (7) trace elements, namely; copper (Cu), nickel (Ni), zinc (Zn), chromium (Cr), vanadium (V), strontium (Sr) and zirconium (Zr) were studied in fifty (50) soil samples randomly sampled from the three locations between 3rd to 10th March, 2014, following EDXRF analyses. The soil samples were analysed with Shimadzu tube-excited EDX 800HS spectrometer available at Material Research Testing Laboratories in the Ministry of Transport, Infrastructure Housing and Urban Development. Multivariate analysis was done on the results of trace elements concentrations using Principal Component Analysis, Cluster Analysis and Regression Analysis so as to determine the predominant element and inter-elemental associations in the samples analyzed. In general, the study found the following trace elements variations; that zirconium had the highest concentration (599-2917) mg/kg, and nickel had the lowest concentration ranging from (6.88-35.8) mg/kg in the study area. In addition, the concentrations of copper, zinc, chromium, vanadium and strontium were found to vary between (16.3-85.1) mg/kg, (10.9-161) mg/kg, (38.7-93.3) mg/kg, (293-657) mg/kg, and (70.3-770) mg/kg, respectively. The elevated concentrations of Zr and V in the soil samples were attributed to their significant role as mineral indicators of buried minerals. Additionally, the Pearson correlation coefficient between Cr and V, Ni and V, Ni and Cr were found to be highly correlated; with R values of 0.64, 0.569 and 0.515, respectively. This was linked to the presence of primary minerals pyroxene and biotite in the underlying geological strata. Moreover, Principal Component Analysis (PCA) qualitatively identified three key clusters which represented the sampling locations, namely; PC1 (87%)-Yoonye, PC2 (11%)-Kateiko and PC3 (1%)-Kathonzweni areas. This explains the difference of three different soil types;